Climate and Building Design

Climate and Building Design
Temperate Climate
Hot Dry Climate
Warm Humid Climate
World Meteorological Organisation Headquarters- Design Innovation

Warm Humid Climate

Summers in this climatic zone are warm, rainy and uncomfortably humid. The body's natural cooling system (the evaporation of perspiration) does not work well, because the air is already so full of water vapour that it limits drying. Winters are warm, dry and sunny. Coastal areas may be subject to tropical cyclones. North of the tropic of Capricorn, the sun will be in the southern sky during summer.

Design Aims
In this humid climate you need to maximise cooling through ventilation and minimise building heat gain.

The building block

• Does your block have access to the prevailing wind in summer?
  This is crucial. Windy spots are best - the tops of hills, on the coast (think about tropical cyclones, though - check our tropical cyclone brochure to find out if TC's are likely in your chosen spot). Look at the path that summer breezes will take to reach your block - a smooth path will exert less frictional drag on the moving air, so air passing over water or flat, cleared land will move faster than if it passes over a built-up suburban area. Windward sides of the hills will be breezier than lee sides.

Your house

• Window alignment and house orientation to catch summer breezes?
  Check the wind-rose chart for the place nearest your house site.

1. What is the usual direction of the summer breeze in your area?
   
   Note that local effects can mean that wind directions vary over short distances. Often a trade-off must be made between ventilation and minimal heat gain. For example, in Darwin the prevailing wind during the wet season is from the NW, so to maximise cross-ventilation, the house should be oriented with the long sides of the building facing NW-SE. On the other hand, solar heat gain is minimised by orientating the house with the long axis running east-west. This minimises the size of the eastern and western walls, which are difficult to shade from the sun. Overhanging eaves easily shade north and south walls. To maximise ventilation on a housing block that sees predominately NW or SE winds, the long axis of the house should face the breeze, that is facing NW-SE. Over most of Darwin for example, which sees predominately either NW or SE winds, this orientation could maximise cross-ventilation through most of the year. Such an orientation may increase solar exposure of house walls though, in which case remedial designs could be considered, such as wide eaves or verandas, or appropriate vegetation shading potentially exposed walls. If local conditions block these breezes, it may be more desirable to minimise heat-load on the walls by orientating the house east-west.
   
   
2. Do you have a long, narrow floor plan in sleeping zone, to maximise through ventilation in bedrooms?
   
   
   
3. Open-plan living areas, to maximise air movement?
   
   
4. Window types which allow good airflow?
   
   Louvres offer the maximum ventilation and modern versions have greatly improved weather resistance. Unlike all other window types, casement windows can be used to catch breezes blowing parallel to the window, so are a good choice when the summer wind direction is variable. Double-hung (sash) windows offer a choice between high and low-level ventilation. Awning (hopper) windows can be left open in wet weather but their ventilation potential is poor.
   
   
5. Elevated construction to catch the breezes.
   In areas prone to tropical cyclones, there is a trade-off - construction cost increases.
   
   
6. Extra ventilation from ceiling fans, rotary vents and wind traps?
   
   
7. Boundary fences which allow airflow?
   A low wire fence is preferable to a high brick wall.
   
   
8. Air movement around your house so that mosquitoes and sandflies will be less likely to linger? They prefer still air.
   
   
9. Is your house of light construction?
   Light materials like timber, fibro sheet will cool quicker at night. Because the night-to-day temperature swing is quite small in this climate, heat-storing materials such as bricks and concrete are of little benefit, particularly in bedrooms where they will make your house warmer at night.
   
   
10. Is your house's heat gain minimised by:
    1. orienting the long axis of the house east-west? The long north- and south-facing walls can easily be shaded by the eaves;
    2. windows on east and west walls kept to a minimum?
    3. shading for the walls and windows - use shutters, verandahs, canopies and/or eaves and fixed overhangs?
    4. using pale colours for walls and roof, to reflect the heat of the sun?
    5. reflective foil insulation?
       It reflects incoming sunshine. Bulk insulation like pink batts is less desirable, because it prevents the house cooling down at night.
       An exception - air-conditioned houses need bulk insulation.
       
       
11. Does your house have spacious outdoor living areas?
    Shelter from the rain is needed in summer - verandahs or under the elevated house, some shade also desirable
    

The Garden

1. Does it allow breezes through the house?
   
   In this sticky climate where breezes are most important, vegetation does not have the overwhelming benefits for comfort that it has in a hot dry climate. While shade is still desirable, it is not quite so important in this climate's cloudy summer and the natural evaporative cooling effect of plants is limited by the damp atmosphere. The wind-sheltering effect of trees is definitely not a plus in this climate. On the other hand, unshaded paved areas absorb and store the sun's heat, making them undesirable next to your house. Most people will want vegetation around their house, - it looks good, the birds need it and it provides shade. The best compromise is to use small plants on the side of the house from which the summer breezes approach, and to make sure that plants don't impede the flow of air through windows.